Modeling of ammonia/air non-premixed turbulent swirling flames in a gas turbine like combustor

In the present study, burner-stabilized non-premixed turbulent ammonia (NH3)/air flames were succeeded using swirling flows, and moreover, the present study found that NO emission is significantly decreased with an increase in pressure in either non-premixed or premixed flames. Because, at high pressure, third body reaction of OH + H + M H2O + M has high sensitivity, and thereby, OH concentration reduction in high pressures leads to the reduction of NO generation, because OH radicals play an important role when amidogen (NH2) is oxidized to NO through nitroxyl (HNO) in the reaction sequence. However, in non-premixed flames, especially in rich conditions, NO emissions are slightly higher than that of premixed flames, because NO production is depended on the local equivalence ratio of the flame region in the non-premixed flames. Thus, there is a significant NO production in the lean flame regions, in which near to the wall boundaries, owing to the high concentration of OH even in the overall-rich flame conditions. In order to avoid this distress, the present study suggests to use split NH3 streams around the air stream, and thus, minimum NO emission was resulted when volumetric ratio, between inner and outer NH3 swirlers, is 0.6: 0.4.